Known is an inkjet recording apparatus for jetting ink onto a recording medium to record an image thereon while an endless belt conveys the recording medium. The recording medium is in close contact with an exterior surface of the endless belt by electrostatic absorption or an adhesive agent applied to the exterior surface of the endless belt.
In the case of conducting a recording operation by conveying a recording medium in the inkjet recording apparatus, there is a case that due to inferior conveyance of the recording medium, ink is jetted onto the belt, not onto the recording medium. Further, in the case of recording, what is known as a borderless image, whereby ink is jetted onto the area which is a little bit wider than the size of the recording medium, so that ink is also jetted onto the belt around the recording medium.
If the ink jetted onto the exterior surface of the endless belt is allowed to adhere onto the rear surface of the recording medium, it lowers the recorded image quality. Further, since the ink lowers the surface resistance of the belt, the problem occurs that the belt decreases a force to adhere the recording medium, and conveyance capability of the recording medium deteriorates. Thus, up to now, a cleaning device has been provided to remove the ink adhered on the endless belt.
With respect to the method for removing the ink adhered on the endless belt, known is a method of rasping off said ink by sliding on and rubbing the moving belt surface while conveying the belt by contact of an elastic plate member, such as a wiper blade, made of rubber or plastic. In order to stabilize the sliding and rubbing force, the elastic plate member is pressed against the exterior surface of the endless belt at a predetermined force.
When the plate member is used as a cleaning means, if the plate member is always in contact with the belt, the conveyance system tends to become deformed by the pressing force of the plate member, which tends to deteriorate the image quality. Further, since the plate member is always forced in a single direction, the plate member can be deformed, which deteriorates its cleaning capability.
In order to overcome the above problems, the thickness of the plate member may be increased, or alternatively the elasticity of the plate member may be increased, so that the plate member tends to straighten itself due to its inherent elastic force, but the pressing force becomes greater on the surface of the endless belt, resulting in an effect opposite the desired one.
Further, there is a case in which the belt is driven in a direction opposite a normal conveyance direction due to paper jams, and a case in which even when the normal recording operation is conducted, after the recording medium is conveyed for a predetermined distance, the belt is driven in the opposite direction to convey the recording medium for the predetermined distance. In addition, the normal conveyance direction means a recording direction. That is, when the belt is driven in the opposite direction, and if the plate member is always in contact with the surface of the belt, the plate member is forced to bend. Since the plate member has elasticity exhibiting a predetermined pressing force, the plate member receives an unreasonable load, which can result in damage to the plate member and the belt.
Due to this, in the conventional art, the plate member is controlled to not always be in contact with the surface of the belt, and is controlled to contact the surface of the belt only when the belt is to be cleaned.
For example, by providing a wiper to scratch and drop the ink adhered on the belt surface and an absorbing member to clean the residing ink droplets left on remaining tracks of the wiper edge on the belt so as to be capable of contacting with and separating from the belt, the wiper and the absorbing member are in contact with the belt only when a cleaning sequence is conducted after the jam is detected, which overcomes the problem in the case that the wiper and the absorbing member are always in contact with the belt, which is disclosed in Unexamined Japanese patent Application Publication No. 3-227,648. Further, by providing a wiper to scratch and drop the ink adhered on the belt surface and an absorbing member to clean the residing ink droplets left on tracks of the wiper edge on the belt so as to be capable of contacting with and separating from the belt, the wiper and the absorbing member are made to contact the belt only when the recording operation is not conducted, which overcomes the problem in the case that the wiper and the absorbing member are always in contact with the belt, which is disclosed in Unexamined Japanese patent Application Publication No. 4-31,070.
In the case when conducting belt cleaning by contacting a cleaning member with the belt only when conducting a cleaning sequence after having detected a jam as, disclosed in Unexamined Japanese Patent Application Publication No. 03-227,648, since belt cleaning is not executed during normal recording operation, the ink, which has adhered onto the belt during normal operation, such as when recording a borderless image onto the recording material, cannot be cleaned off at all.
On the other hand, in the case when conducting belt cleaning by contacting the cleaning member with the belt only during a non-recording period, as proposed in Unexamined Japanese Patent Application Publication No. 04-31,070, since belt cleaning is not executed during normal recording operation, in case when continuously recording images onto a long recording material, such as textile outputted from rolled original textile, cleaning is not executed for a long period of time. Thus, since the recording material is conveyed when the belt surface is dirty, it is hard to avoid staining of the recording medium. Further, in case when the non-recording operation period does not coincide with the necessary time period for cleaning, the belt surface cannot be cleaned. When a recording operation is stopped until a cleaning operation is completed, the image recording productivity is reduced.
Further when the cleaning member is mechanically contacted with and separated from the belt surface, if the belt is conveyed at a high velocity to raise the recording productivity, the number of contact-separating operation of the cleaning member against the belt per a unit-time becomes large. Thus, there is a problem that mechanical operation sound level of the contact-separating operation becomes high.
Further, since a plurality of cleaning members are contacted with and separated from the belt, the maintenance work for stably operating the cleaning device for a long time becomes complicated.